Top changer contact bridge with spring-biased lost motion pin connection



y 29,1969 GI.WITTENLZELLYNER 3,458,670

TAP CHANGER CONTACT BRIDGE WITH SPRING-BIASED LOST MOTION PIN CONNECTION Filed July 5, 1967 2 Sheets-Sheet 1 y 29, 1969 G. WITTENZELLNER 3,458,670-

TAP CHANGER CONTACT BRIDGE WITH SPRING-BIASED LOST MOTION PIN CONNECTION v Filed July 5, 1967 2 Sheets-Sheet 2 M h l r... 5 1 2. l/afi/ 4 a I F flaw m a 0 W W W United States Patent US. Cl. 20011 7 Claims ABSTRACT OF THE DISCLOSURE The contact bridge disclosed herein is an improvement of the contact bridge disclosed and claimed in US. Patent 3,238,318 to A. Bleibtreu et a1. Mar. 1, 1966 for Concact Bridges for Radial Contacts with Fulcrum and Resilient Spring Structure. A greater freedom of movement is imparted to the contact bridge resulting in reduced wear of the contacts and an improved self-cleaning action of the latter. The increased freedom of movement is achieved by a spring-biased lost motion pin connection between the contact bridge proper and the contact bridge support. The contact bridge is primarily intended for so-called Jansen type transfer switches and in connection with tapped regulating transformers, but has also many other applications.

Background of the invention The above referred-to US. Patent 3,238,318 shows a contact bridge which equalizes the degree of erosion due to arcing occurring at two serially related points of break, and establishes a resilient support for the movable contacts which are supported by it. In the structure of US. Patent 3,238,318 there are two pairs of serially related contacts, including two fixed contacts and two movable contacts. The pair of serially related contacts which is subject to a relatively small degree of erosion is caused to part first, and the pair of serially related contacts which is subject to a relatively larger degree of erosion is caused to part last. Thus, in the long run, i.e. considering a relatively large number of switching operations, the degree of erosion of both serially related pairs of contacts is maintained reasonably, or substantially, equal.

It is desirable to provide contact bridges, and more particularly contact bridges for Jansen type transfer switches, wherein the above referred-to performance characteristics are present, and wherein, in addition thereto, the movable contacts are adapted to perform a combined sliding and tilting motion relative to their c0- operating fixed contacts resulting in a wiping action. The present invention is a solution to the aforementioned problem.

US. Patent 2,833,873 to B. Jansen; May 6, 1958 for Multiple Tap Switch Construction for Changing Transformer Taps Under Load refers to a Jansen type transfer switch including means for effecting a contact wiping action. The transfer switch disclosed in this patent is adapted to form single breaks rather than series breaks at each point of break, and this is a serious limitation of the structure of US. Patent 2,833,873 to which structures embodying the invention are not subject.

Summary of invention The structure embodying this invention comprises two pairs of contacts including a first and second fixed contact and a first movable contact cooperating with said first fixed contact and a second movable contact cooperating with said second fixed contact. It further includes a contact bridge supporting said first and said second movable contact. The contact bridge is pivotally supported on a contact bridges support and the latter is attached to operating means for jointly moving the contact bridge support and the contact bridge relative to said first and said second fixed contacts. The structure is further provided with torque imparting means responsive to the difference between the degree of erosion of said first fixed contact and said first movable contacts and to the degree of erosion of said second fixed contact and said second movable contact to selectively tilt said contact bridge about said pivotal support thereof in either of two different directions upon joint movement of said contact bridge support and said contact bridge relative to said first fixed contact and said second fixed contact. The above pivotal support is constructed in such a way that it allows composite pivotal movements of the contact bridge relative to the contact bridge support in two planes enclosing right angles, thus resulting in a sliding and tilting motion of the first movable contact when engaging the first fixed contact and of the second movable contact when engaging the second fixed contact.

Brief description of the drawings In the drawings:

FIG. 1 is in part a top plan view and in part a horizontal section of a transfer switch for a Jansen type tapchanging regulating transformer allowing tap-changes to be effected under load conditions;

FIG. 2 is a vertical, partly diagrammatic section of the fixed contacts and the movable contacts of the structure of FIG. 1 when parted from each other, FIG. 2 being diagrammatic inasmuch as the fact that the cooperating surfaces of the fixed contacts and of the movable contacts enclose an acute angle when parted from each other is not shown in FIG. 2;

FIG. 3 shows the same structure as FIG. 2 in the same fashion as FIG. 2, but shows the closed position rather than the open position of its contacts, FIG. 3 being a section along III-III of FIG. 1;

FIG. 4 is substantially a section along IVIV of FIG. 2 showing some parts in top-plan view rather than sectionalized, and showing the angular relation of the cooperating surfaces of the fixed contacts and of the movable contacts when parted from each other; and

FIG. 5 shows the same structure as FIG. 4 in the same fashion as FIG. 4 but refers to a point of time when the cooperating surfaces of the fixed contacts and of the movable contacts are not completely parted from each other but just begin to engage each other.

Description of preferred embodiment Referring now to the drawings, numeral 1 has been applied to indicate a cylindrical insulating support for the fixed contacts of a Jansen type transfer switch. These contacts are arranged in pairs, each pair being arranged along a generatrix of the cylindrical support 1 for the fixed contacts. The contacts of each pair of fixed contacts are arranged at different levels, as clearly shown in FIGS. 2 and 3. All the fixed contacts arranged at the higher level 'form an arcuate or sector-like pattern, and all the fixed contacts arranged at the lower level form an arcuate or sector-like pattern. The fixed contacts include two pairs of main contacts 2 and four pairs of auxiliary contacts 3. The auxiliary contacts 3 are arranged between the main contacts 2. Thus the former may also be referred to as inner fixed contacts and the latter as outer fixed contacts. The pairs of fixed contacts 2, 3 may 'be connected to a tapped transformer winding (not shown) and to switching resistors (not shown) in the way described in considerable detail in US. Patent 3,176,089 to A. Bleibtreu et al.; Mar.

30, 1965 for Load Tap Changers for Transformers and in U.S. Patent 3,23 8,320; Mar. 1, 1966 for Transfer Switch for Tap Changers for Regulating Transformers Including a Cylindrical Insulating Housing, a Squirrel Cage Contact Supporting Structure and Contact Bridges Insulatingly Supported by Contact Bridge Carriers and also described in the paper by Rudolf Klaus, Untersuchungen an Last- W'zihlernund Lastumschaltern (System Dr. Jansen) fiir grosse Schaltlaufigkeit (Investigations on selector switches fiand transfer switches-System Dr. Jansenfor highly repetitive duty) Elektrotechnische Zeitschrift, Part A, vol. 81, pp. 67-74.

Each pair of fixed main contacts 2, 2 may be engaged by a pair of movable main contacts 12, 12 and each pair of fixed auxiliary contacts 3, 3 may be engaged by a pair of movable auxiliary contacts 5, 5. Contacts 12 may part from contacts 2, and contacts 5 may part from contacts 3. Engagement and parting of contacts 2, 12 and 3, 5 must be effected in a predetermined sequence by appropriate contact operating mechanisms which are Well known in the art and, therefore, need not be described in considerable detail. The required sequence of operation of movable contacts 12, 5, 5, 5, 5, 12 depends upon the type of tap-changing circuitry which has been adopted and is set forth in considerable detail in the aforementioned U.S. Patent 3,238,320 and the aforementioned paper. The movable contacts 12, 5, 5, 5, 5, 12 may be operated by means of an operating mechanism designed along the lines set forth in the aforementioned U.S. Patent 2,833,873.

The movable main contacts 12 of which one is shown at the top of FIG. 1 as being in engagement with one of fixed main contacts 2 perform a composite motion when parting from fixed main contacts 2. To be more specific, they perform a radially inward motion with respect to cylindrical contact support 1, and they perform, in addition thereto, a rotary motion with respect to contact support 1. When the main contacts 12 of which one is shown at the top of FIG. 1 as being in engagement with one of fixed main contacts 2 have completed the opening stroke thereof, main contacts 12 are shifted in counterclockwise direction as seen in FIG. 1 and moved radially inwardly. This position is analogous to that of movable contacts 12 of which one is shown at the bottom of FIG. 1 in the open position thereof.

All the movable contacts 12 and 5 are operated by operating arms or push rods 6, and are supported by the latter at the radially outer ends thereof. The support of auxiliary contacts 5 by arms or rods 6 may be effected in any conventional manner and, therefore, does not need to be considered in this context. Movable main contacts 12 are supported by operating arms or rods 6 in a novel fashion, embodying this invention, and the way in which contacts 12 are supported by arms or rods 6 will be explained below in detail.

The radially inner ends of arms 6 form bearings 6a and are mounted on a common shaft 8 which is pivotable in opposite directions, as indicated by arrows A. Reference numeral 7 has been applied to indicate vertical rods arranged parallel to contact support 1 for operating and guiding contact operating arms 6. Rods 7 are tied together (by means not shown) to form an integral structure which is pivoted jointly with shaft 8-. The radially outer ends of arms 6 supporting movable main contacts 12 are provided with U-shaped insulating elements 9 each including a Web portion and two flange portions. The latter extend substantially radially outwardly and expose the front surfaces or contact surfaces of movable main contacts 12 to allow engagement thereof with contacts 2. Reference character 9' has been applied to indicate U-shaped insulating elements arranged at the radially outer ends of the arms 6 which support the movable auxiliary contacts 5.

The movable main contacts 12 are supported by a part 11 which will hereinafter be referred to as contact bridge. Contact bridge 11 is, in turn, supported by contact bridge support 11, and the latter is affixed to the radially outer ends of a pair of arms 6. The support of contact bridge 11' by its support 11 is effected by the intermediary of a pair of sinusoidally shaped leaf springs 14 whose ends rest in knife edge bearings provided in contact bridge 11 and contact bridge support 11, respectively. This kind of spring suspension of contact bridge 11' is described in greater detail in the aforementioned U.S. Patent 3,238,318.

Reference numeral 4 has been applied to generally indicate the structural unit comprising the pair of movable main contacts 12, the contact bridge 11', the pair of leaf springs 14 and the contact bridge support 11. Contact bridge 11' is further supported by contact bridge support 11 by means of a pin 13 projecting transversely through parts 11 and 11'. Contact bridge 11 defines a recess or cavity 11", and contact bridge support 11 defines a boxlike structure, or spring housing 15 projecting into recess or cavity 11". Pin 13 is arranged midway between the ends of contact bridge 11. The surface of spring housing 15 juxtaposed, or immediately adjacent to, contact bridge 11 forms a groove receiving the right surface of pin 13 (as seen in FIGS. 2 and 3). The vertical lateral surfaces of spring housing 15 are provided with oblong holes 16, and the axially outer ends of pin 13 project through oblong holes 16 into contact bridge 11. Contact bridge 11' is substantially U-shaped in cross-section (FIGS. 4 and 5 The outer surface of its web portions supports movable main contacts 12. The aforementioned recess or cavity 11" is bounded by the two flange portions of contact bridge 11'. The two flange portions of contact bridge 11' form bearings receiving the axially outer end of pin 13. Spring housing 15 accommodates the leaf spring 17. Leaf spring 17 engages with its center portion a groove-like recess 18 provided in pin 13. Leaf spring 17 includes two substantially U-shaped or hair-pin-shaped end portions each having a flange resting against the surface of spring housing 15 remote from contact bridge 11'. As a result, spring 17 biases contact bridge 11 from left to right, as seen in FIG. 2, or, in other words, away from contact bridge support 11.

As clearly shown in FIGS. 2 and 5, the support 11 for each contact bridge 11 and each pair of contacts 12 comprises two parts separated by an insulating layer 20. Thus arms 6 are insulated from contacts 12.

It will be apparent from the foregoing that contact bridge 11 may pivot about pin 13, this pivotal motion occurring in a vertical plane. As a result of the presence of the oblong holes 16 in contact bridge support 11 contact bridge 11' may move or pivot jointly with pin 13 in a horizontal plane. Any such motion is effected against the action of spring 17 acting against pin 13 and tending to maintain pin 13 and contact bridge 11' in the position shown in FIG. 2.

When contact bridge support 11 and contact bridge 11 are moved to their contact closed positions, contacts 12 engage contacts 2 and spring 17 exerts a predetermined contact pressure. When movable contacts 12 are moved into engagement with fixed contacts 2, pin 13 moves within oblong holes 16, loading spring 17, and causing spring housing 15 to move into recess or cavity 11". This is clearly shown in FIG. 3 and the upper main contacts 2, 12 of FIG. 1 are shown in the same position as shown in FIG. 3.

FIGS. 4 and 5 illustrate more fully a closing operation of main contacts 12. It is apparent that the juxtaposed surfaces of contacts 2, 12 enclose an acute angle at the point of time immediately preceding the engagement thereof. A a result, contacts 2 and 12 engage initially only along their edges. (FIG. 5). Thereupon pivot 13 moves inside oblong holes 16, resulting in a horizontal tilting motion of contacts 12, and of contact bridge 11', relative to contact bridge support 11. This tilting motion has been indicated in FIG. 5 by arrows B. At the end of that tilting motion the juxtaposed surfaces of contacts 2, 12 are in fully abuting relation as shown in FIG. 3.

It will be apparent from the foregoing that the structure embodying this invention results in a relatively soft or smooth engagement of contacts 2 and 12 tending to limit their wear, and that contacts 2 and 12 engage under a wiping action, and are thus self-cleaning.

The compensation of uneven erosion of contacts 2, 12 is effected under the action of leaf springs 14, as more fully disclosed in the aforementioned US. Patent 3,238,318. The operation of leaf springs 14 in equalizing erosion of contacts 2, 12 will be briefly outlined below:

As long as upper contacts 2, 12 and lower contacts 2, 12 are not eroded by arcing, contact bridge 11' remains in its vertical position shown in FIGS. 2 and 3, i.e. it does not pivot about pin 13 in clockwise direction or counterclockwise direction, as seen in FIGS. 2 and 3. This is true irrespective of whether upper contacts 2, 12 and lower contacts 2, 12 are engaged, or out of engagement. Such a pivotal motion takes place when the erosion of the pairs of cooperating contacts 2, 12 is unequal. Then bridge 11' and contacts 2, 12 are caused to pivot about pin 13 relative to bridge support 11, the pair of serially related contacts 2, 12 which is subject to a relatively small degree of erosion parting first and the other pair of serially related contacts 2, 12 parting last, thus equalizing the degree of contact erosion, considering a large number of successive switching operations.

It will be understood that the structure embodying this invention is not limited to tap-changing transfer switches for regulating-transformers, or to Jansen type transfer switches. This structure is useful in many applications involving contact bridges having a pair of movable contacts cooperating with a pair of fixed contacts, all contacts being serially connected into an electric circuit, when it is desired to equalize contact erosion, to maintain cooperating contacts in a clean condition by a wiping action of cooperating contacts, and to cushion the impact of the movable contacts upon the fixed contacts by spring action.

In FIG. 5 a straight arrow indicates the direction in which part 6 operates bridge support 11. This direction encloses an obtuse angle with the front surface of fixed butt contact 2 cooperating with movable butt contact 12. Pin means 13 is floatingly supported in oblong holes 16, i.e. pin means 16 is free to perform any kind of motion within the general plane defined by registering oblong holes 16 within the limits determined by the length of oblong holes 16. Leaf springs 14 yieldingly maintain bridge support 11 and contact bridge 11' in a predetermined relative position shown in FIG. 2.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim as my invention:

1. In an electric switching device the combination of:

(a) a pair of fixed spaced butt contacts each having a contact surface;

(-b) a pair of movable butt contacts each having a contact surface engageable with and separable from said contact surface of one of said pair of fixed contacts;

(c) a contact bridge supporting at substantially opposite ends thereof said pair of movable contacts;

(d) a support for pivotally supporting said contact bridge thereon;

(e) operating means for said support for operating said support and said contact bridge in directions enclosing an obtuse angle with said contact surface of each of said pair of fixed contacts;

(f) spring means interposed between said contact bridge and said support for yieldingly maintaining said contact bridge and said support in predetermined relative positions;

(g) pin means pivotally supporting two points of said contact bridge on said support to allow pivotal motions relative to said support;

(h) means defining a pair of oblong holes each receiving one end of said pin means to allow in addition to said pivotal motion of said contact bridge relative to said support free floating motions of said pin means within the general plane defined by said pair of oblong holes within limits determined by the length of said pair of oblong holes; and

(i) additional spring means supported by said support engaging said pin means at the center region between the ends thereof and biasing said pin means and said contact bridge away from said support.

2. An electric switching device as specified in claim 1 wherein said pair of oblong holes is defined by said support, and wherein said additional spring means is formed by a leaf spring having a center portion hugging the periphery of said pin means and two substantially U- shaped end portions each in abutting engagement with said support.

3. An electric switching device as specified in claim 1 wherein said spring means is formed by a pair of leaf springs having ends resting in knife-edge bearings, wherein said contact bridge defines a recess at the side thereof remote from said pair of movable contacts, wherein said support for said contact bridge defines a spring-receiving chamber projecting into said recess and having lateral walls defining said pair of oblong holes, said spring-receiving-chamber housing a leaf spring having a center portion in engagement with and hugging the periphery of said pin means and two substantially U-shaped end portions each in abutting engagement with a surface of said spring-receiving chamber remote from said contact bridge.

4. An electric switching device as specified in claim 1, wherein said pin means is provided with a spring-receiving groove midway between the ends thereof, and wherein said spring means is formed by a bent leaf spring having a center portion engaging said spring-receiving groove and end portions in abutting engagement with said support for said contact bridge.

5. In a transfer switching device of the Jansen type the combination of:

(a) a plurality of pairs of spaced fixed contacts, each of said plurality of pairs of fixed contact being arranged along a generatrix of a cylindrical surface, said plurality of pairs of spaced fixed contacts including two pairs of outer fixed contacts and pairs of inner fixed contacts;

(b) a plurality of pairs of spaced movable contacts, each pair of said plurality of pairs of movable contacts having a pair of contact surfaces engageable with, and separable from, one of said plurality of pairs of fixed contacts, said plurality of spaced movable contacts including two pairs of outer movable contact and pairs of inner movable contacts;

(c) a pair of substantially channel-shaped contact bridges each supporting one of said two pairs of outer movable contacts on the web surface thereof and each being provided on the flange surfaces thereof with a pair of coaxial pin-receiving holes;

((1) a pair of contact bridge supports each supporting one of said pair of contact bridges and each defining a spring-receiving chamber in the region substantially midway between the ends thereof, said springreceiving chamber of each of said pair of supports having lateral walls juxtaposed to the flange surfaces of one of said pair of contact bridges, said lateral walls being perforated by a pair of registering oblong holes therein;

(e) a pair of operating means each for one of said pair of supports each imparting to one of said pair of supports a composite rotational and radial motion;

(f) a pair of pins each pivotally securing one of said pair of contact bridges to one of said pair of sup ports, each of said pair of pins projecting through said spring-receiving chamber in one of said pair of supports and through said oblong holes thereof into said pin-receiving holes in the flange surfaces of one of said pair of contact bridges;

(g) two pairs of leaf springs, each of said two pairs of leaf springs being arranged at opposite sides of one of said pair of pins and each of said two pairs of leaf springs being interposed between one of said pair of contact bridges and one of said pair of support for yieldingly maintaining each of said pair of contact bridges and one of said pair of supports in predetermined relative positions; and

(h) an additional pair of leaf spring each arranged in said spring-receiving chamber of one of said pair of supports, each of said additional pair of leaf springs having a center portion hugging the periphery of the center portion of one of said pair of pins and each having substantially U-shaped end portions abutting against a wall of said pin-receiving chamber in one of said supports whereby each of said pair of pins may freely move against the bias of one of said additional pair of leaf springs within a plane defined by said pair of oblong holes in each of said pair of supports.

6. In an electric switching device the combination of;

(a) a pair of fixed spaced contacts arranged along a vertical line;

'(b) a pair of movable contacts arranged along a vertical line each having a contact surface engageable with and separable from said pair of fixed contacts;

(c) a substantially channel-shaped contact supporting bridge supporting at opposite ends of the web portion thereof said pair of movable contacts and having a pair of coaxial passages in the flange portions thereof, said bridge defining a cavity bounded by said flange portions at the side thereof remote from said pair of movable contacts;

(d) a support for said contact supporting bridge arranged generally parallel to said contact supporting bridge, said support having a hollow projection engaging said cavity in said contact supporting bridge and defining a spring-receiving housing including a pair of laterals walls having a pair of oblong horizontla perforations arranged at the same level as said horizontal passages in said flange portions of said contact supporting bridge;

(e) a horizontal pin arranged in said spring receiving housing and extending across said oblong perforations in said flange portions of said contact supporting bridge and having axially outer ends engaging said pair of coaxial passages in said flange portions of said contact supporting bridge;

(f) operating means for said support for operating said support and said contact supporting bridge in directions enclosing an obtuse angle with the contact surface of each of said pair of fixed contacts;

(g) a pair of spring means arranged at opposite sides of said pin each interposed between said contact supporting bridge and said support for yieldingly maintaining said contact supporting bridge and said support generally parallel; and

(h) an additional leaf spring arranged in said springreceiving housing of said support for said contact bridge having a center portion engaging the periphery of said pin in the center region thereof, said additional leaf spring having U-shaped end portions abutting against the wall of said spring-receiving housing remote from said contact bridge whereby said additional leaf spring biases the freely floating movement of said pin Within the plane defined by said pair of oblong perforations.

7. An electric switching device as specified in claim 6 including a vertical pivot, operating arm means pivotable about said pivot, said arm means supporting said support for said contact supporting bridge at the end thereof remote from said vertical pivot, and a substantially U- shaped member of insulating material having a web portion arranged in a vertical plane and having flange portions arranged in vertical planes, said web portion being situated at the end of said arm means remote from said vertical pivot and said flange portions overlapping said support for said contact supporting bridge, and said contact supporting bridge, and exposing said contact surface of each of said pair of movable contacts.

References Cited UNITED STATES PATENTS 2,356,836 8/ 1944 Ebert. 3,154,662 10/ 1964 Heupel et al. 3,238,318 3/1966 Bleibtreu et al. 200-10 FOREIGN PATENTS 210,964 2/ 1960 Austria. 1,151,059 7/1963 Germany. 637,200 10/ 1936 Germany. 1,168,541 4/1964 Germany. 1,175,336 8/1964 Germany.

ROBERT K. SCHAEFER, Primary Examiner ROBERT A. VANDERHYE, Assistant Examiner U.S. Cl. X.R. 200-153, 164, 166 

